Method of manufacturing lithium secondary battery

Abstract

Disclosed is a method of manufacturing a lithium secondary battery. A polymer mixture including a) polyvinylidene fluoride-based polymer and b) at least one polymer selected from the group consisting of polyacrylonitrile and polymethyl methacrylate is mixed with a solvent in which a lithium salt is dissolved. The mixing ratio of the polymer mixture and the solvent is about 1:3-10. Thus obtained first mixture is heated to obtain a polymer electrolyte composition. And this polymer electrolyte composition is coated onto a first electrode which is one of an anode and a cathode, and then dried to obtain a polymer electrolyte layer. Then, a second electrode which is a remaining one of the anode and cathode is attached onto the polymer electrolyte layer. The polymer electrolyte has a good mechanical strength and the lithium secondary battery has a stable charge/discharge characteristic.

What is claimed is:  
     
       1. A method of manufacturing a lithium secondary battery comprising the steps of: 
       mixing a polymer mixture including a) polyvinylidene fluoride-based polymer and b) at least one polymer selected from the group consisting of polyacrylonitrile and polymethyl methacrylate with a solvent in which a lithium salt is dissolved, said polymer mixture and said solvent being mixed in a mixing ratio of about 1:3-10;  
       heating thus obtained first mixture to obtain a polymer electrolyte composition;  
       coating thus obtained polymer electrolyte composition on a first electrode which is one of an anode and a cathode, and then drying to obtain a polymer electrolyte layer; and  
       attaching a second electrode which is a remaining one of said anode and cathode onto said polymer electrolyte layer.  
     
     
       2. A method of manufacturing a lithium secondary battery as claimed in  claim 1 , wherein said drying is implemented at a temperature range of from room temperature −60° C. for a time period of 1 minute-1 hour. 
     
     
       3. A method of manufacturing a lithium secondary battery as claimed in  claim 1 , wherein said polymer electrolyte composition is coated on said first electrode to a thickness range of 20-100 μm. 
     
     
       4. A method of manufacturing a lithium secondary battery as claimed in  claim 1 , wherein said first electrode is larger than said second electrode. 
     
     
       5. A method of manufacturing a lithium secondary battery as claimed in  claim 1 , wherein a viscosity of said polymer electrolyte composition is in the range of 1,000-50,000 cps. 
     
     
       6. A method of manufacturing a lithium secondary battery as claimed in  claim 1 , wherein said second electrode is attached with said polymer electrolyte layer by applying a pressure of 0.01-100 N/cm 2 . 
     
     
       7. A method of manufacturing a stacked lithium secondary battery comprising the steps of: 
       mixing a polymer mixture including a) polyvinylidene fluoride-based polymer and b) at least one polymer selected from the group consisting of polyacrylonitrile and polymethyl methacrylate with a solvent in which a lithium salt is dissolved, said polymer mixture and said solvent being mixed in a mixing ratio of about 1:3-10;  
       heating thus obtained first mixture to obtain a polymer electrolyte composition;  
       coating thus obtained polymer electrolyte composition on a first surface of a first electrode which includes the first surface and a second surface and is one of an anode and a cathode, and then drying to obtain a polymer electrolyte layer;  
       coating said polymer electrolyte composition on the second surface of said first electrode;  
       attaching a second electrode which is a remaining one of said anode and cathode with said polymer electrolyte layer to obtain a unit cell;  
       stacking a plurality of said unit cells to obtain a multi-layered cell;  
       impregnating said multi-layered cell with a predetermined amount of a liquid electrolyte; and  
       packaging thus obtained multi-layered cell.  
     
     
       8. A method of manufacturing a lithium secondary battery as claimed in  claim 7 , wherein said first electrode is larger than said second electrode. 
     
     
       9. A method of manufacturing a wound lithium secondary battery comprising the steps of: 
       mixing a polymer mixture including a) polyvinylidene fluoride-based polymer and b) at least one polymer selected from the group consisting of polyacrylonitrile and polymethyl methacrylate with a solvent in which a lithium salt is dissolved, said polymer mixture and said solvent being mixed in a mixing ratio of about 1:3-10;  
       heating thus obtained first mixture to obtain a polymer electrolyte composition;  
       coating thus obtained polymer electrolyte composition on a first surface of a first electrode which includes the first surface and a second surface and is one of an anode and a cathode, and then drying to obtain a polymer electrolyte layer;  
       coating said polymer electrolyte composition on the second surface of said first electrode;  
       attaching a second electrode which is a remaining one of said anode and cathode with said polymer electrolyte layer and then winding;  
       impregnating said winding cell with a predetermined amount of a liquid electrolyte; and  
       sealing thus obtained winding cell.  
     
     
       10. A method of manufacturing a lithium secondary battery as claimed in  claim 9 , wherein said first electrode is larger than said second electrode.